1. Field of the Invention
This invention relates to metal casting technology and particularly to the casting of complex Vee configuration engine blocks.
2. Description of the Prior Art
Cast iron engine cylinder blocks of the Vee configuration are typically cast in one of two positions, either an upsidedown position in the mold (sometimes referred to as pan rail up) or in an upright position (often referred to as in the car position). The mold cavity for these blocks is split along a horizontal parting plane forming an upper and a lower mold portion, and is comprised of compacted grain sand which is molded over a male pattern. A limitation of this mold forming process is that any flanges, ribs or bosses on the sides of the engine block casting must be drafted or loaded in the direction that the pattern is withdrawn from the mold. On Vee configuration blocks having an included angle of about 90.degree., this limitation results in a weight penalty. On 60.degree. Vee configuration cylinder blocks this weight penalty is even more severe due to the narrower bank angle and the need for various stiffening ribs at the transmission end of the block. An illustration of the conventional manner of making Vee configuration engine blocks is shown in U.S. Pat. No. 2,783,510. It shows the extent to which drafting must be exaggerated to accommodate Vee angles, here being 110.degree., and thus resulting in a weight penalty.
To eliminate some of such loading from bosses and stiffening ribs, thereby creating a weight penalty, the prior art has resorted to using mold inserts in the form of side mold parts which will define the necessary side wall features of the casting. While these additional mold inserts provide product features at a lesser weight, they do significantly increase the variable cost of the casting due to the need to produce handle and set additional mold inserts in the mold assembly.
What is needed is a process of casting such Vee configuration blocks so that the draft angle for flanges, ribs or bosses can extend in a direction transverse to the axis of the Vee angle and yet eliminate the necessity for mold inserts of any type while eliminating unnecessary weight additions due to accommodating unnecessary draft angles and, at the same time, increasing productivity of a given size refractory mold by permitting a greater number of castings to be made in such given mold.